Nuclear Matrix Protein 1 (NXP1)

RAD21 is highly similar to the gene product of Schizosaccharomyces pombe rad21, a gene involved in the repair of DNA double-strand breaks, as well as in chromatid cohesion during mitosis. This protein is a nuclear phospho-protein, which becomes hyperphosphorylated in cell cycle M phase. The highly regulated association of this protein with mitotic chromatin specifically at the centromere region suggests its role in sister chromatid cohesion in mitotic cells. RAD21 is expressed in the nucleus at the same level throughout the cell cycle and that it becomes hyperphosphorylated during M phase. Immunofluorescence microscopy demonstrated that RAD21 begins to dissociate from arm region chromatin during prophase and from centromere regions during metaphase and anaphase and is associated with spindles.